Code integrity check for centralized traffic control systems



F. ALBRIGHTON CODE INTEGRITY CHECK FOR CENTRALIZED TRAFFIC CONTROL SYSTEMS May 18, 1954 4 Sheets-Sheet 1 Filed Feb. 26, 1952 IN VEN TOR.

RfAlbr'ighton BY Hi5. ATTORNEY May 18, 1954 R. F. ALBRIGHTON CODE INTEGRITY CHECK FOR CENTRALIZED TRAFFIC CONTROL 5Y$TEMS 4 Sheets-Sheet 2 Filed Feb. 26. 1952 INVENTOR. REAIbrighton.

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H is ATTORNEY May 18, 1954 R. F. ALBRIGHTON 2,679,034

com: INTEGRITY CHECK FOR CENTRALIZED TRAFFIC CONTROL SYSTEMS Filed Feb. 26, 1952 4 Sheets-Sheet I5 MMWV,

H is ATTORNEY y 8, 1954 R. F. ALBRIGHTON 2,679,034

CODE INTEGRITY CHECK FOR CENTRALIZED TRAFFIC CONTROL SYSTEMS Filed Feb. 26, 1952 4 Sheets-Sheet 4 FlaAA.

' CONTROL OFFICE TRANSMISSION 5m. RIGHT i i Fl 6.4B.

FIELD STATION RECEPTION LINE ARK- AW ARK-q-MARWPACHJPACE-PMARH CSPI I I I D I 1V1 2V1 1' 5V1 4V1 i 2M M l I 4M u 6M I 1 T 6M 5 F 1 1 7M EXEW TION L SOLID BAR REPRESENTS ENEPGIZATION "COMMUNICATION OF5WITCH CYCLE CODE INVENTOR MAR-K MARKMARK MARK SPACE SPACE MARK BY RfAlbm-ghton His ATTORNEY Patented May 18, 1954 CODE INTEGRITY CHECK FOR CENTRAL- IZED TRAFFIC CONTROL SYSTEMS Reginald F. Albrightcn, Rochester, N. Y, assignor to General Railway Signal (Jumpany, Rochester, N. Y.

Application February 26, 1952, Serial No. 273,373

7 Claims.

This invention relates to the checking of the integrity of codes in a code communication system of the type used in centralized traffic control systems for railroads, and it more particularly relates to means for preventing the execution of a switch and/ or signal control code transmitted from a control office to a field station, upon reception at the field station, in case of a failure of a transmitted code to check with the code that has been designated to be transmitted.

The present invention is of utility in a code communication system such, for example, as that disclosed in the prior application of N. B. Coley, Ser. No. 240,086, filed August 3, 1951, which has resulted in Patent No. 2,626,314, dated January 20, 1953. In this system the transmission of codes is by marks and spaces, a mark being a period of energization of a line circuit, or a period of modulation for carrier or space radiation transmission, and a space being a period of deenergization or no modulation, as the case may be. Thus the transmission of the code from the control ofiice is by the pulsing of a transmitter relay, which, when actuated to one position, closes the line circuit for the transmission of a mark, and when actuated to the other position, opens the line circuit for a space character.

Generally speaking, and without attempting to define the scope of the present invention, the present invention provides a check relay for insuring the integrity of mark and space character transmission. The check relay is required to be maintained energized at the control ofiice, dependent upon a continuity check through the code selecting circuits during the respective steps. Should there be a failure of continuity, the check relay would be actuated, and its actuation would so affect the termination of the cycle of operation of the code communication system as to forestall execution of the code received at a field sta tion during the cycle of operation.

An object of the present invention is to distinctively characterize the code transmitted during a cycle of operation of a code communication system to prevent the execution of the code as received in case th code transmitted does not correspond to a predetermined code that has been designated for transmission.

Another object of the present invention is to require a check relay at a transmitting station to be maintain d picked up throughout the transmission of a control code in order to transmit a distinctive final character permitting execution of the code when received at a field station, the energization of the check relay being dependent during the respective steps upon the continuity of code character selecting circuits during the respective steps selecting either mark or space characters.

Other objects, purposes, and characteristic features of the present invention, will be in part obvious from the accompanying drawings, and in part pointed out as the description of the invention progresses.

In describing the invention in detail, reference is made to the accompanying drawings, in which corresponding parts are designated by like referenc characters; in which similar parts having similar functions are designated by like letter reference characters generally having preceding numerals indicative of the order of the relay operation and succeeding numerals indicative of designation of a distinctive location or station with which the apparatus is associated, and in which:

Figs. 1A and 113 when placed end to end illustrate schematically the system organization of one embodiment of the present invention wherein the organization as illustrated in Fig. 1A is of apparatus located at the control ofiice, and wherein the part of the system illustrated in Fig. 1B is at a field location;

Fig. 2 is a schematic diagram illustrating the organization for the operation of a typical stepping relay bank that can be used in connection with the present invention;

Fig. 3 is a sequence diagram illustrating the times of operation of the respective stepping relays as measured by their associated oscillatory timing device; and

Figs. 4A and 4B are diagrams illustrating particularly the normal sequence of relay operation at control ofiice and field stations, respectively, during a control cycle.

Conventional schematic diagrams have been used for the disclosure of the system organization in the drawings, such drawings being prepared more particularly to facilitate an understanding of the mode of operation of the system, rather than to attempt to point out all of the necessary details of construction and specific arrangement of components that may be provided by those skilled in the art in accordance with the requirements of practice. The symbols (-1-) and have been used to indicate connections to the respective positive and negative terminals of suitable batteries or other sources of direct current.

Although it is to be understood that the present invention is readily adaptable for the communication of switch and signal controls from a control office to a remote field station for a track layout having a relatively large number of track switches and signals to be controlled, for the purpos of simplification of this embodiment of the present invention,ithas been considered suflicient for an understanding of the present invention that it be applied only for the control of a single track switch and signals overning trafilc thereover, which may be considered, for example, as a small part of a larger railway interlocking system, other track switches and signals being governed by respective controls transmitted from the control oflice in a similar manner from that which will be hereinafter specifically considered for the control of the single track switch and signals that are illustrated in Fig. 13. According to Fig. 13, a main stretch of track 20 is illustrative as having a second track 2| connected thereto by a track switch AW which is operated by a power switch machine lSM. Eastbound trafiic over the track switch 4W is governed by signals 2A and 23, while westbound trafiic over the track switch 4W is governed by the signals 3A and 313.

It is to be understood that the system includes a suitable control machine at the control office, such as is well known in the art, for governing traflic through the track layout. This machine has a suitable control panel (not shown) having a track diagram constructed thereon with suitable indicator lamps (not shown) being disposed along the trackway of the diagram for indicating the conditions of occupancy of the respective track sections Within the controlled territory. Indicator lamps (not shown) are also provided on the control panel in accordance with the requirements of practice for indicating the positions of track switches, the locked conditions of the track switches, and the conditions of the signals governing trafiic through the track layout for which the control machine is provided. Also disposed on the control panel, either directly on the track diagram, or below the track diagram, in accord ance with the requirements of practice, are suitable levers or buttons for designation of the entrance and exit ends of routes to be established, or for designation of the positions of the track switches and signals to be controlled. Thus, for example, with reference to Fig. 1A, a switch control lever ESML is provided for the control of the track switch 4W (see Fig. 1B) and the signal control lever 2-3SGL is provided for controlling the clearing of the signals governing traffic through the track switch 4W. The lever iSlViL is a twoposition lever, the left-hand position as shown in Fig. 1A being used for governing the power operation of the track switch 4W to its normal position, and the right-hand position of the lever 4SML being used for governing the power opera tion of the track switch 4W to its reverse position. The signal control lever 2-3SGL is a threeposition lever wherein its center position is used for putting the associated signals to stop, its lefthand position is used for governing the clearing of a signal for governing westbound traflic, and its right-hand position is used for governing the clearing of a signal for governing eastbound traffic. It is to be understood that these switch and signal control levers may be replaced by other types of manually operable switches, or by relays, or by buttons or any other suitable means that may be desired to be employed in practice for the designation of the controls that are to be transmitted for the control of respective track switches and signals.

Although different types of timing devices may be used for governing the rate of operation of the stepping, the timing device employed in this embodiment of the present invention is illustrated in Fig. 2 as being of the torsional pendulum, or balance wheel type of the general character disclosed in the patent to O. S. Field, No. 2,351,588, dated June 20, 1944. This oscillator, according to the Field patent, is adapted to be driven at a constant rate and to be energized for a limited period of each of its operating cycles so as to maintain its oscillations continuously at a uniform rate as long as energy is applied to the device. For the purpose of driving the stepper used in this em bodiment of the present invention, however, it is considered more desirable that the oscillator mechanism be normally inactive but retained in a predetermined one of its extreme rotated positions so that it can be started from a predetermined contacting position when it is desired to initiate the stepping operation at the associated station. Therefore the oscillator according to the Field patent is preferably modified to provide that its winding is normally energized as is illustrated in Fig. 2 when the system is at rest, and upon setting the code communication system into operation, energy is removed from the electromagnet of the associated oscillator CT and the torsional pendulum, or balance wheel, is permitted to oscillate freely, the amplitude and periodicity of which is determined by the inertia of the balance wheel in combination with the characteristics of an involute spring such as the spring illustrated in Fig. 2.

For the purpose of simplification of the disclosure of the present invention, certain parts of the system which can be provided comparable to corresponding identified parts in the above mentioned Coley application have not been shown in detail, as reference can be made to this Coley application for a detailed consideration of these parts. Thus, at the control office, the stepping relays lV, 2V, 3V, and 4V, the cycle start relays CS and CSP, and the cycle repeat relays CP and CPP (see Fig. 1A) have their windings shown only in block form, and it is to be understood that these relays can be controlled by circuit organizations disclosed for similarly designated relays in the above mentioned Coley application.

Similarly at the field station (see Fig. 1B) the stepping relays IVI, ZVl, 3Vl, and 4Vl, the cycle start relays CS I, CSPI, and LCSI, and the indication code transmitter relay Cl are shown only in block form as it is to be understood that circuits for their control can be provided as disclosed for similarly identified relays in the above mentioned application of N. B. Coley.

A cycle start relay CH and an associated relay LC is provided at the control OfilCe for each of the various control levers on the control machine as a means for respectively starting a control cycle of operation of the code communication system, and determining the code for transmission during a cycle of operation. The various relays LC are interlocked by the use of a relay LCS so that only one relay LC can be picked up at one time to prevent interference with the transmission of a selected code, once transmission has been initiated.

A code transmitter relay C is provided at the control ofiice for pulsing a normally energized line circuit which connects the control office and the field station, the line circuit having a line relay L at the control oifice and a line relay Ll at the field station.

The checking of the integrity of code transmission at the control ofiice is accomplished by a check. relay CK which is required to be maintained energized by its respective stick circuits throughout each control cycle in order to permit the transmission of a code which may be exeouted when received at a field station. The sustained energization of the check relay CK during transmission, dependent upon continuity in the respective code character selecting circuits, will be more readily understood as the description progresses and the specific mode of operation of the system is considered.

In accordance with the reception of control codes at the field station illustrated in Fig. 13, message relays 2M, 3M, EM, 5M, and EM are selectively energized in accordance with the reception of a marl; during the steps corresponding to the preceding numerals of these reference characters.

.A. magnetic stick switch control relay evvz is provided at the field station for governing the power operation of the track switch 5W, left and right neutral signal control relays LGZ and RGZ are provided for governing the clearing of signals for the respective opposite directions of traffic through the track switch iW, and the relay 2 B is provided for restoring a signal to stop in accordance with the reception of a signal stop code. The stick circuits for the relays LGZ and RGZ which are usually provided for causing stick operation of the signals are not shown, but they can be provided according to the requirements of practice.

Having thus considered the general organization of the apparatus in a code communication system for one embodiment of the present invention, the circuit organization will be hereinafter more specifically described when considering the mode of operation of the system during typical operating conditions.

Operation Before considering specifically the circuit organization and mode of operation under typical operating conditions, it is believed expedient to consider the mode of operation in general, without specific reference to the circuits involved in such operation.

If it is desired to transmit a control from the control ofice to the field station for setting up a route, the operator of the control machine first actuates all of the switch control levers required for obtaining the proper positions of the track switches to set up a route, and then he actuates the signal control lever SGL (see Fig. 1A) for the signal governing entrance to the route. In accordance with the actuation of these respective levers, an associate-cl relay CH is dropped. away, and the dropping away of this relay is eifective to cause the picking up of the associated relay LC, and the relay LCS. The picking up of the relay LCs prevents the picking up of other relays LC during the control cycle, and it also deenergizes the oscillator CT, and thus sets the oscillator into operation to actuate the stepping relays and selectively govern the energiaation of the code transmitting relay (3 for the transmission of a control code.

With reference to the diagram of Fig. 3, when the torsional pendulum 3&8 of the oscillator CT first rotates through its center osition, the opening of one set of contacts or" the oscillator CT is effective to denergize the first of the stepping relays IV, and similarly for each of the subsequent rotations of the pendulum 388 in the same direction through the center position, an odd numbered stepping relay V is dropped away. Upon the rotation of the pendulum 388 through center in the opposite direction to complete the first excursion of the pendulum 383 with respect to its locked u position, the second step is taken by the dropping away of the relay 2V, and on subsequent similar operations of the oscillator pendulum 388.! in the same direction through center, an even numbered step is taken by the dropping away of an even numbered stepping relay V.

it will be noted with reference to Fig. 4A that during the second excursion of the oscillator pendulum 38% from its initial position, the stepping relay W is picked up in response to the dropping away of relay 3V, so that this relay can be used a second time for defining the beginning of a step. Similarly, the dropping away of relay 3V causes the picking up of relay 2V, so that relay 2V can be used again to form an additional step. The dropping away of relay iv for the second time, during the third excursion of the pendulum 388, causes the picking u of relay 3V, so that this relay can also be used for the second time to form an additional communication channel.

Thus the stepping relays are deenergized successively in numerical order to form the respective steps. the relays IV, 2V, and 3V being used over for the second time to form a complete complement of seven steps when the following distinctive seven conditions of the stepping relays are established;

Stepping Relay it can thus be said that the respective steps are effectively coded in that they are made up of respective distinctive combinations of front and back stepper relay contacts on four relays in seven different combinations, these combinations being so selected for transmission of the code characters in the control circuit for the code transmitter relay C that seven distinctive communication channels are provided for code transmission. Should a greater number of communication channels be required in practice, the number of steps can be increased by the addition of stepping relays. the same condition of a repeat of operation for several of the relays can be employed. selection of the respective code characters for transmission made through these respective channels, and. energy is applied selectively to a maria bus MB or to a space bus SB, the code selected for transmission being in accordance with whichever one of the relays LC that is picked up. For lockout purposes, the first character transmitted the control cities is always a mark, and thus this channel is not used for code communication purposes -ior this embodiment of the presen' invention. The manner in which the mark under these conditions i effective to lock out a simultaneous field station start is fully disclosed in the above mentioned Coley application to which reference can be made for a more complete description of the mode of operation'under these conditions.

At the field location, the line relay LI is normally energized, and the deenergization of this relay in accordance with the start of the transmission of a control cycle at the control ofiice is effective to initiate the operation of the code oscillator CH, and thus initiate the stepping at the field location. This stepping takes place in a manner comparable to the stepping at the control office. Thus the field stepper is not necessarily actuated at the same time as the stepper at the control office. In fact the field stepping is initiated later by the operating time of relay C at the control ofiice and the line relay Ll at the field station, plus whatever line propagation time there may be; but the stepper is actuated. at the same rate as the stepper at the control office because of the code oscillators CT at the respective control office and field locations being accurately matched in their operating characteristics so that when they are permitted to operate in free oscillations upon removal of energy from their respective electromagnets, the rate of operation is the same at both transmitting and receiving stations.

At the field location, a decoding relay M is picked up for each mark that i received during the particular one of the steps with which the relay M is associated, the picking up of this relay being rendered effective in response to the dropping away of the stepping relay for the associated step, provided that the line relay L is picked up at this time. It will be noted with reference to Fig. B that there is no relay llVl' required because the first character transmitted from the control office is always a mark for lockout purposes as has been heretoior considered, and the lookout condition is satisfied in the control of the relay CSP! particularly so not to require a relay M for the reception of t. first character. Each relay M when picked up is maintained energized by a suitable stick circuit until the end of the cycle, subsequent to the execution of the code that has been received in a manner fully described in the above mentioned application of N. B. Coley.

Although other types of execution circuit selections may be employed. in accordance with the requirement of practice, the embodiment of the present invention illustrated in Fig. 13 provides for an execution circuit affording a parity check of the code so as to eliminate to a large extent the possibility of a reception of a garbled code as being effective to actuate any switch or signal control relay. This parity check system requires communication of codes always having an even number of marks (not including the mark for the first step), and the system for the selection of codes for transmission at the control ofiice is so arranged that each code transmitted comprises an even number of marks (not including the mark for the first step). It is thus provided that should a single mark be lost in the transmission of a code so as not to be received at the field location, the reception of an odd number of marks would prevent execution of a code, and thus there would be no switch or signal control relay actuated as the garbled code would be detected by the parity check system to prevent the execution of a faulty code. Similarly if an additional mark were received by picking up energy on the line circuit from an extraneous source during a single period originally employed for the designation of a space, the reception of one additional mark would prevent the execution of a code at the end of a cycle from being effective to control any switch or signal application relay. It is believed that it should be readily apparent that the system could be readily modified if desired to provide for the codes employed as having odd. numbers of marks rather than even numbers, it being a matter of choice as to which form is to be used.

Another condition required to be fulfilled at a field station in order to permit execution is that the line circuit must be deenergized for a short period of time at the time of execution in order that execution can take place. Thus the control office transmitter must open the line circuit for an interval following the transmission of the last character of the code for the cycle of operation in order that the field station may execute the code which has been received and decoded by the selective energization of the mark relays M at the field station.

In view of the foregoing consideration of the requirement for the line circuit to be opened following the code to permit execution, the mode of operation of the check relay CK (see Fig. 1A) at the control ofiice is such that should this relay be dropped away during transmission of a control code because of there being a failure to transmit the designated code, by reason of this relay CK being dropped away during the last part of the cycle, the opening of the line circuit at the end of the cycle to permit execution of the code of the field station is prevented.

From the above described mode of operation, it will be seen that the detection of a garbled transmission at the control oifice is made by the check relay CK, and the actuation of this relay is eiiective by preventing the opening of the line circuit at the end of the cycle to transmit a distinctive condition to the field station forestalling execution of the code that has been received, and thus preventing the possibility of a wrong control being executed for the control of a track switch and/or signal. This check will be recognized as being effective for any number of faulty code characters as compared to the parity check which will not detect a double error.

Having thus described the general mode of operation, more specific consideration will hereinafter be given to the circuit organizations in volved in providing such mode of operation, reliance being made on the detailed disclosure of the above mentioned application of N. B. Coley for disclosure of the parts of the system that are identical to parts employed according to the present application.

Initiation of control cycle Although it should be readily apparent to those skilled in the art that difierent systems of initiation of a control cycle which are known in the art may be employed with a system of this character, the system according to the embodiment of the present invention illustrated in Fig. 1A is organized so that no start buttons are required as the relays CH are so governed by polarized circuits as to be actuated whenever the associated switch or signal control lever is moved to a new position. For providing this mode of operation, the respective switch and signal control levers can be considered circuitwise as pole-changing levers in that each time the lever is actuated to a new position, the circuit for the associated change relay CH is pole-changed through its stick contact so as to cause that relay to be dropped away for the initiation of a control cycle, restoration of the relay being efiected by energy of the newly selected polarity upon the picking 9 up of the associated relay LC when the cycle is actually initiated.

The relay ACI-I, which is associated with the switch control lever ASML, is normally energized by a stick circuit extending from including front contact 22 of relay lCI-l, contact 23 of lever RSML in its left-hand position, and upper winding of relay lCH, to Similarly the relay 2-3CH, which is associated with the signal con trol lever 2-3SGL, is normally energized by a circuit extending from including front contact 2d of relay 2-3CH, contact 255 ofv lever Z-tSGL in its center position and upper winding of relay 2-3CI-I, to

If the lever lSlVEb is moved from its normal to its reverse position (right-hand position), for example, the circuit just described for relay ilCH is pole chan ed by the shifting of the contact 23 for lever tSML, and thus the relay H is dropped away upon energiaation of the lower winding of including winding of relay LCS, such circuit extending from (-1-), including back contact 29 of relay CPP, back contact 3% of relay CP, back contact 3! of relay CSP, front contact 32 of relay CS, front contact 33 of relay L, winding of relay LCS, front contact 34 of relay lLC,

and upper winding of relay ME, to The picking up of relay LCS starts the stepping of the cycle by the deenergization of the oscillator CT opening the circuit by which the oscillator CT normally energized at back contact 555 (see Fig. 2). The circuit by which the oscillator CT is normally energized extends from including front contact 35 of relay CS, front contact 3? of relay L, back contact 3.5 of relay LCS, and winding of oscillator CT, to

The relays lLC and LCS (see Fig. 1A) are maintained energized throughout the control cycle by the stick circuit that has been described, together with other stick circuits wherein front contact of relay 055?, back contact 33 of relay CS, and front contact at of relay LCS shunts the front contacts 3:2 33 or relays CS and L, and the back contacts t9, and El of relays CPP, CSP, respectively, out of the stick circuit cat has just been described. Another shunting stick circuit is provided by the closure of front contact s: of relay W in series'with front contact id of relay LCS. The relay iLC when picked up is effective by the closure of front contact 42 to establish pickup for the relay lCH extending from including front contact 43 of relay LCS, front contact 42 of relay lLC, contact 23 of lever AlSlViL in its right-hand position, and lower winding of relay lLC, to

Having thus considered specifically the mode of operation upon initiation or" a cycle of operation in accordance with the actuation of the lever -'3SML to its right-hand position for designation of the track switch 1W to be operated to its re verse position, it should be readily apparent from the description as set forth that a similar mode of operation is effected upon actuation of the lever ist/ill in the opposite direction for the designation of the track switch QW to be operated to its normal position, the actuation of the lever 10 lSML in either case being efiective to pole change the relay 501-1 and thus cause that relay to be dropped away so as to initiate the control cycle.

The initiation of a control cycle for the transmission of a signal control is similarly efiected in that the actuation of the three-position signal control lever 2-3SGL to any new position is effective to pole change the associated change relay 2-3CH and thus cause that relay to be dropped away so as to effect the picking up 0:. the relays 2-3LC and LCS. Thus, for example, the actuation of the lever 2-3SGL to its right-hand position for governing the clearing of signal 2 for eastbound traffic pole changes the relay 2-3CH which has been described as having its upper winding normally energized through the contact 25 of the lever i-BSGL in its center position.

The movement of the lever 2-3SGL in either direction from its center position opens the circult for the upper winding of the relay Z-SCH at contact '2 5, and establishes a circuit for the energization of the lower winding with the opposite polarity. Thus, for example, if the lever 2-3SGL is actuated to its right hand position for designation of a signal to be cleared for eastbound traffic, the lower winding of relay 2-301-1 is momentarily energized by a circuit extending from including front contact 24 of relay 2-3CH, contact 25 of lever 2-3SGL in its right-hand position, and lower winding of relay .2tCfl, to This energization is of a polarity to oppose the flux previously set up by energization of the upper winding, and thus the relay ii-SCH is dropped away, and the circuit just described is opened at front contact 2i.

Upon the dropping away of relay t-BCH, if the system is at rest, the relay Q -SLC can be picked up by the energization of a circuit extending from including front contact is of relay C, back contact 2'? of relay LCS, front contact 28 of relay iCI-I, back contact 44 of relay Z-SCH, and lower winding of relay 2-6130, to Relay 2-3LC, when picked up, causes the picking up of relay LCS by the energization of a circuit extending from (-1-), including back contacts 29, 3t, and 3| of relays CPP, GP, and CSP, respectively, front contact 32 of relay CS, front contact 33 of relay L, winding of relay LCS, front contact to of relay 23LC, and upper winding of relay Z-BLC, to

After the picking up of the relay LCS in accordance with the picking up of relay 2-3LC, the relay E-BCI-I is restored to its picked up position by the energization of a circuit extending from including front contact it of relay LCS, front contact 45 of relay Q-SLC, contact 25 of lever 2-3SGL in its right-hand position and lower winding of relay Z-ECI-I, to

The line circuit comprising the line wires 4'! and 48' connecting the control oilice and the hold location is normally energized by a circuit extending from the positive terminal of the line battery LB through back contact to of relay CK, front contact to of relay CS, winding of relay line wire 48, winding of relay Ll, front contact 5| of relay Cl, and line wire ll, to the negative terminal of the line battery LB.

Message transmission The selection of the code characters used for transmission is in accordance with whichever one of the relays LC (see Fig. ill) at the control office has been picked up, This is because each of the characters transmitted, except for the first character which is always a mark, is determined by a circuit through a front contact of a relay LC, only one relay LC being picked up at a time in 11 accordance with the chain circuit organization for the picking up of the relays LC as has been heretofore considered. Thus the relay 4LC when picked up, for example is illustrated as having contacts which determine as to whether the respective characters transmitted during a control cycle are marks or spaces in accordance with a predetermined code. If energy is applied through these contacts to a mark bus MB the character transmitted is a mark, and if the character selected for transmission is a space, energy is applied to the space bus SB rather than the mark bus MB. Tthe first group of code characters transmitted is used for identifying the particular device to be controlled according to the present embodiment, and the last group of characters is used for identifying the particular position to which the device selected by the first group of characters is to be operated. Thus the relay 4L0 when picked up selects a first group of characters comprising respectively three marks and a space identifying the track switch 4W as the device to be controlled, and the last two characters determine the position to which the track switch lW is to be operated in accordance with whether the lever 48M is in its normal or reverse position. Thus the control code for transmission of a reverse control for the track switch 4W comprises the characters "mark-mark-mark-space-spacemark. This is in addition to the first character which is always a mark as has been heretofore described. If the control code to be transmitted is for the operation of the track switch lW to its normal position, the code selected for transmission by the relay MC in combination with the lever lSML being in its left-hand position is "mark-mark-mark-space-mark-space.

The character transmitted during the first step is always a mark because of the closure of a circuit applying energy to the mark bus MB through contact fingers 52 and 53 of oscillator CT, front Contact 54 of relay LCS, front contact 55 of relay 2V, and front contact 55 of relay 4V.

With relay lLC picked up, the bus MB is energized for the transmission of a mark during the second step through contact fingers 57 and 58 of oscillator CT, front contact 59 of relay LCS, back contact 60 of relay IV, front contact BI of relay 3V, front contact 62 of relay llV, front contact 63 of relay 4L0, and jumper 64.

The character transmitted during the third step is a mark because of energy applied to the bus MB through contact fingers 52 and 53 of oscillator CT, front contact 54 of relay LCS, back contact 55 of relay 2V, front contact 65 of relay 4V, front contact 66 of relay QLC, and jumper 61.

During the fourth step a mark is transmitted because of energization of bus MB through contact fingers 51 and 58 of oscillator CT, front contact 59 of relay LCS, front contact 66.] of relay IV, back contact 68 of relay 3V, front contact 69 of relay ALC, and jumper 10.

With relay lLC picked up, the character transmitted during the fifth step is a space because of the energization of the bus SB through contact fingers 52 and 53 of oscillator CT, front contact H of relay LCS, front contact 72 of relay 2V, back contact E3 of relay 4V, front contact is of relay lLC, and jumper I5.

If it is assumed that the lever 4SML has been actuated to its right-hand position for the designation of the track switch iW to be operated to its reverse position, the character transmitted during the sixth step is a space because of energy applied to the space bus SB through contact -12 fingers 5? and 58 of oscillator CT, front contact 59 of relay LCS, back contact 66 of relay IV, front contact SI of relay 3V, back contact 62 of relay 4V, front contact 76 of relay ILC, and con tact ll of lever ESML in its right-hand position.

The character transmitted during the seventh step, with the lever ASML in its right-hand position, is a mark because of application of energy to the bus MB through contact fingers 52 and 53 of oscillator CT, front contact I! of relay LCS, back contact 2 of relay 2V, back contact I8 of relay 4V, front contact 19 of relay ALC, and contact 88 of lever IlSML in its right-hand position.

Should a normal switch control be designated for transmission by the actuation of the lever lSML to its left-hand position, the selected energization of the respective mark and space buses MB and SB would be as has been described except that the last two characters are respectively mark and space as provided by an obvious selection by the contacts H and 80, respectively, of the lever SSML.

In accordance with the application of energy to the mark bus MB, the relay C is picked up by the energization of its lower winding through front contact 8| of relay LCS and front contact 8m of relay CK, this relay being dropped away upon the initiation of a control cycle by the opening of its normally energized circuit for its upper winding at back contact 82 of relay LCS. The circuit by which the relay C is normally energized extends from including front contacts 83, 84, 85 and 86 of relays 4V, 3V, 2V, and IV, respectively, back contact 82 of relay LCS, and upper winding of relay C, to Relay C when energized during any step is maintained energized until the oscillator CT next changes the position of its contacts as its pendulum 338 (see Fig. 2) rotates through center. The actuation of the contacts of the oscillator CT at the end of the first step, for example, opens the circuit for the energization of relay C at contact fingers 52 and 53, and the subsequent dropping away of the relay 2V at the beginning of the second step further opens the circuit for relay C at the front contact 55 to prevent energization during subsequent steps, the inclusion of front contact 56 or relay 4V being effective to maintain the circuit open during the last part of the cycle when the relay 2V is restored to its picked up position and used for a second time during the cycle. Similarily after each of the other steps is taken, the prior circuit for the energization of the relay C is opened and maintained opened for the remainder of the cycle of operation.

Each time that a space is to be transmitted, the space bus SB is energized as has been described, and no energy is applied to the mark bus MB, thus for the corresponding step the relay C is in its dropped away position so as to open the line circuit at front contact 81, the energization of the space bus SB being effective to apply stick energy to the upper winding of relay CK through front contact 88 for purposes to be hereinafter fully described.

Immediately upon the picking up of relay LCS at the beginning of a control cycle, a pickup circuit is closed for the check relay CK extending from including contact fingers 51 and 58 of oscillator CT, front contact 59 of relay LCS, front contact 65 of relay IV, front contact 63 of relay 3V, and upper winding of relay CK, to The selection of the pickup circuit for the relay CK is such that it is opened as soon as the stepping is initiated, and is maintained open for the remainder of the stepping operation. Thus the continued energization of the relay CK is dependent entirely upon energy applied to its stick circuit, except for slightly slow acting characteristics provided by the shunting of the lower winding of the relay CK through front contact 89. It has been pointed out that the relay CK is energized whenever a space is selected as a code character by application of energy to the space bus SB, and it is also provided that the relay CK has stick energy whenever the relay C is picked up for the transmission of a mark. This energy is applied through front contact 90 of relay C, front contact s! of relay LCS, and front contact 88 to the upper winding of relay CK.

From the circuits just described for the energization of relay CK, it will be noted that as long as energy is applied selectively to the bus MB or the bus SE for each step during transmission, the stick circuit for the relay CK is maintained substantially continuously energized, the only period of deenergization being the crossover time of a stepping relay contact in going from one step to the next, and the relay CK is maintained picked up for this short interruption of energy by reason of the shunting or" its lower winding through the contact 89. It will therefore be seen that the relay CK checks circuit continuity through the respective channels that are used for setting up the respective predetermined codes, and should itact in this continuity circuit fail to close, wire becomes loose, or the like, preventing the up of the relay C for the transmission of a mark character when such character should transmitted, there will be no energy applied at the time of transmission of the character to the space bus SB, because it is a mark that has been selected for transmission, and by reason of the relay C failing to pick up, stick energy will be interrupted for the check relay CK at front contact 90 of relay C, and the relay CK will become dropped away for the remainder of the cycle of operation.

Because of the relay CK becoming dropped away during the cycle, it must remain dropped away from the remainder of the cycle, and in accordance with this mode of operation, the relay CK will hold the line circuit closed at the control oflice through back contact 49 of relay CK, so as to in effect cause all mark characters to be transmitted for the remainder of the cycle,

irrespective of the pulsing of contact ill of relay C in series with the front contacts t2 and 93 of relay LCS. In other words, the back contact d8 of relay CK is arranged in the line circuit to render the selective pulsing of the line circuit ineffective in accordance with the pulsing of the relay C for the remainder of the control cycle. Relay CK is prevented from picking up at the end of the cycle when the stepping relays are restored, because the relay LCS is dropped away prior to the restoration of the stepping relays, and thus the opening of front contact 59 of relay LCS in the pickup circuit for relay CK prevents the picking up of relay CK at the end of a control cycle. Similarly it will be recognized that energy feeding the respective MB and SB buses must also be applied through respective front contacts of relay LCS, and therefore these buses become deenergized upon the dropping awayof relay LCS at the end of the cycle. The dropping away of relay LCS, the associated relay LC, is rendered eifective at the end or" the control cycle by the picking up of the relay CS to open the stick circuit for relay LCS at back contact 39. The mode of operation of the relay CS in picking up at this time is fully disclosed in the i i above mentioned prior application of N. B. Coley. With the relay CS picked up, and the relay CK dropped away, the normal conditions or" energization are restored for the line circui For the purpose of calling the attention of an operator to the abnormal condition of transmission, the buzzer B2, or a comparable indi cating device, is sounded. Thus i relay CK becomes dropped away during code transmission the buzzer 32 becomes energized a circuit in-- cluding back contact 5553 of relay C, back contact [5 2 of relay CK, and front contact 555 of relay LCS. The energization of this circuit is only momentary because of the dropping away 01' relay ICE; and the picking up of relay C at the end or" the cycle. If desired, however, stick control requiring the manual acknowledgment of the abnormal condition to open the circuit for the buzzer be added according to the requirements of practice. For normal operation, the buzzer never sounds at the end or a cycle because relay CK is slow in dropping away and front contact 55 of relay LCS is open before Hit of relay becomes closed.

back contact Reception of controis With referez "e to 1B, the line relay Ll is indicative g the respective steps of a control cycle as to whether the respective charac ters received are marks or spaces with reference to stepping by the field stepping relay bank as driven by its associated oscillator C'li. Thus upon reception of the code, a mark relay IJI is picked up for each step (except the first) in response to the actuation of the corresponding stepping relay, provided that the line Li. is picked up at this time to register that mark is being received over the line circuit.

It is therefore provided that upon the dropping away of the second step relay El/"i, the relay 2M is picked up, provided that the line circuit is energized at this time. The pickup circuit for the relay 2M extends from (-1 including back contact t l of relay front contact of relay Ll, contact fingers as and hi or" oscillator CTl, back contact 93 of relay ii/"i, back contact as of relay 2V5, front cont ct Hit of relay Vi, and lower winding of relay to The relay 2l /l when picked up is maintained energized until after the execrion ind at the end of the cycle by a circa eluding front contact liii of r l y CS'fi, front ct Edi: of relay 2M. 2e relay CSPl has been u, in response to the dropping of relay Vi during the first step by the energization of a circuit extending from including contact ringers H53 tilt of oscillator ccntact of relay hi, or contact 95 of relay iVl, front Contact of relay ZVl, front contact Hit; of relay l'Vi, back: iceof LCSi, and lower wi ding of relay CSii, to It will be noted that the C8393 be icked up by the pickup circuit just described only provided that the front ontact of the line relay Li is closer. This is a redui o for the reception of a control cycle in case of sin rub taneous control office and field sta" markthe beginning of the third time period in the reception of a code the field location, the

relay SM is picked, up, if a mark is received during this time period. The circuit for the energization of relay 3M extends from including back contact 3-! of relay LCSI, front contact 95 of relay Ll, contact fingers H and Ill of oscillator CTi, back contact HZ of relay 2V5, back contact H3 of relay 3W, front contact H l of relay iVI, and lower winding of relay 3M, to The picking up of this relay establishes an obvious stick circuit at front contact H to maintain this relay picked up until the end of the cycle.

Upon the dropping away of the relay lVi to mark the beginning of the fourth time period in the reception of a code at the field location, the relay 4M is picked up, if a mark is received during this time period. A circuit for the energization of relay GM extends from including back contact 96 of relay LCSi, front contact 95 of relay Ll, contact fingers 96 and 9? of oscillator CTE, front contact 53 of relay lVi, back contact I lb of relay iVI, and lower Winding of relay iVi to The closure of front contact ll? of relay 4M establishes a stick circuit to maintain relay QM energized for the balance of the control cycle.

If the line circuit is energized at the time when the fifth step is taken, the relay 5M is picked up. The pickup circuit for the relay 5M extends from including back contact 34 of relay LCSI, front contact 95 of relay Ll, contact fingers H0 and III of oscillator CTI, back contact H8 of relay IVI, front contact H9 of relay 2Vi, back contact I20 of relay iVl, and winding of relay 5M, to The picking up of this relay closes front contact i2! to maintain the relay 5M picked up until the end of the cycle.

Relay 6M can be picked up during the sixth step, if the line circuit is energized, in accordance with the energization of a circuit extending from including back contact M of relay LCSI, front contact 95 of relay Ll, contact fingers 96 and 91 of oscillator CTi, back contact 98 of relay IVI, back contact 99 of relay 2Vl, back contact 560 of relay GVl, front contact E22 of relay BVI, and lower winding of relay GM, to The closure of front contact I23 of relay EM maintains this relay energized for the remainder of the control cycle.

If a mark is received on the seventh step, the relay TM is picked up upon the dropping away of the relay 3V8 for the second time to form the seventh step. The circuit for the energization of relay EM extends from including back contact 94 of relay LCS i front contact c5 of relay Ll, contact fingers l 29 and i i of oscillator CTI, back contact H2 of relay 2Vl, back contact H3 of relay 3Vl, back contact ii l of relay iVi, and lower winding of relay TIM, to The picking up of this relay establishes a stick circuit at front contact I24 to maintain relay I'M picked up until the end of the execution period.

Execution To consider the execution of a particular code, it will be assumed that the code mark-markmark-space-space-mark (in addition to the mark transmitted during the first step) has been transmitted for the power operation of the track switch 4W to its reverse position. The reception of this code causes energization as has been described of the decoding relays 2M, 3M, 2M, and TM. The beginning of the execution period is defined by the picking up of the relay CS1, this relay being picked up in response to the pas sage of the rotating mechanism of the oscillator CTI through center for the last time during the cycle of operation. Thus the relay CSi is picked up at this time by the energization of a circuit extending from including contact fingers I25 and I26 of oscillator CTl, back contact 12'! of relay 3Vl, back contact i28 of relay EVi, back contact I29 of relay lVl, and upper winding of relay CSI, to Relay CSi when picked up is maintained energized during the execution period by a stick circuit including front contact I39 of relay CSPI, and front contact 539 of relay CS1. This stick circuit maintains the r lay CSI picked up until the relay Ll is picked up at the end of the cycle to close a stick circuit through front contact I32 by which the relay CS1 is normally energized. Relay CSPI is energized with the relay CS! picked up through back contact N3 of relay 2Vi, front contact 53:!- of relay 08!, and back contact 109 of relay LCSi. Thus the relay CSPI and CS! are maintained picked up until the restoration of the stepping relays to their picked up positions at the end of the cycle so as to open the circuit just described for relay CSPI at back contact 133 of relay 2Vi.

With the relays CSPi and CS! both picked up, one of the requisites of an execution period is fulfilled, the other requisite being that the line relay Ll be dropped away. This is in accordance with the general mode of operation that has been described wherein execution of a control code that has been received can be prevented by the abnormal dropping away of the check relay CK at the control office so as to maintain the line circuit closed during the last part of the control cycle and thereby provide that the line relay LI at the field sttaion is maintained picked up, and is thus effective to prevent execution of the code that has been received by maintaining the execution circuit open at back contact :95.

To consider the specific circuit organization for the exectuion of a particular control, it will be assumed that the code has been received as has been described for the power operation of the track switch 3W to its reverse position, and with the line relay Li dropped away and the relays CSI and CSPi both picked up, the magnetic stick switch control relay lWZ is energized with a polarity to drive it to its dropped away position by a circuit extending from including back contact 86 of relay LCSi, back contact of relay Ll, front contact 235 of relay CSE, front contact i323 of relay CSPI, back contact E3? of relay CPI, front contacts N8, :38, and Hit of relays 2M, 3M, and QM, respectively, back contact id! of relay 5M, back contact N2 of relay 6M, front contact 53 of relay 7M, front contacts M5, M15, and 246 of relays 2M, 3M, and cm, respectively, back contact i i? of relay 5M, back contact Mt of relay 6M, front contact MS of relay 5M, front contact I 50 of relay iWZ, and upper winding of relay flWZ, to The shifting of the contacts l5| and 52 of relay iWZ pole changes the switch control circuit governing the power operation of the switch machine QSM and thus causes the power operation of the track switch 4W to its reverse position.

Should the code calling for the power operation of the track switch 3W to its reverse position be received without the short period of deenergization of the line circuit at the time of execution, the line relay Li would not be dropped away during execution, and the relay 4W2 could not be energized as has been described through back contact 95 of relay Ll. Thus receiving the switch trol code for transmission, said code of selected mark and space characters determining means being effective when actuated to initiate the code communication system into a cycle of operation, circuit means selected by said code determining means for selectively applied energy to respective mark and space buses in correspondence with respective mark and space characters determined by said code determining means for transmission, a code transmitter relay, circuit means for energizing said code transmitter relay each time energy is applied to said mark bus, a check relay, pick up circuit means for said check relay momentarily energized in response to actuation of said manually operable means, stick circuit means for maintaining said check relay energized whenever said code transmitter relay is energized, and whenever a space code character is selected for transmission, means including said check relay for abnormally conditioning said line circuit at the end of transmission of a control code in a control cycle during which said check relay has become deenergized during code transmission, decording means at the iield station responsive to the code transmitted from the control office during a cycle of operation, and code execution means at the field station for causing the operation of said particular device in accordance with the respective control code that has been received over said line circuit from the control oifice, said code execution means being rendered ineffective to govern said device at the end of a control cycle in case said check relay at the control oflice has abnormally conditioned said line circuit.

4. A centralized trafiic control system for the communication from a control ofiice to a field station of respective normal and reverse controls for a two position device comprising in combination, manually operable means at the control of" ac positioned in accordance with designated normal and reverse positions respectively for said device, normally at rest code communication apparatus including a line circuit connecting the control. office and the field station, said apparatus having a code transmitter relay at the control ofiice for acting upon said line circuit, a code deter mining relay at the control OffiCB eiTective when energized in combination with said manually operable means to determine the respective code characters forming respective selected codes for the control of said device, circuit means for energizing said code determining relay in response to the actuation of said manually operable means, circuit means for energizing said code transmitter relay for each character of a particular type selected for transmission by said code determining relay, a check relay at the control ofiice, pick up circuit means for said check relay momentarily energized in response to actuation of said manually operable means, stick circuit means eiiective to maintain said check relay energized during the transmission of code characters only so long as said trainsmitter relay is energized for each character of said particular type of the code characters determined by said code determining relay and said manually operable means, means including said code communication apparatus and said check relay for abnormally conditioning said line circuit at the end of a control cycle during which said check relay has become deenergized during code transmission, and code execution means at the field station for causing the operation of said device to its respective normal and reverse positions in accordance with the respective normal and reverse switch control codes received over said line circuit, said code execution means being rendered inefiective to govern said device at the end of a control cycle upon the reception at the field station of said abnormal characterization of the line circuit.

5. A centralized traflic control system for the communication from a control office to a field station of controls for a device having a plurality of distinctive controllable conditions comprising in combination, selector means at the control office positioned in accordance with designated respective controllable conditions for said device, normally at rest code communication apparatus connecting the control ofiice and the field station having a code transmitter relay at the conrol oilice, a code determining relay at the control ofiice efiective when energized in combination with said selector means to determine the respective code characters forming respective selected control codes for said device, circuit means for energizing said code determining relay in response to the actuation of said selector means, circuit means for energizing said code transmitter relay for each character of a particular type selected for transmission by said code determining relay, a check relay at the control oflice, pick up circuit means for said check relay momentarily energized in response to actuation of said manually operable means, stick circuit means effective to maintain said check relay energized during the transmission of code characters only so long as said transmitter relay is energized for each character of said particular type of the code characters determined by said code determining relay, means including said code communication apparatus and said check relay for distinctively characterizing transmission to said field station upon completion of the stepping at the end of a control cycle in case said check relay becomes deenergized during the transmission of a control code in the associated cycle of operation, and code execution means at the field station for causing the operation of said device to its respective controllable conditions in accordance with the respective control codes received, said code execution means being rendered ineiiective to govern said device in response to said distinctive characterization of the code communication apparatus.

6. A centralized trafiic control system for the communication from a control ofiice to a field station of controls for a device having a plurality of distinctive controllable conditions comprising in combination, manually operable means at the control oflice for designation of respective desired controllable conditions of said device, normally at rest code communication apparatus connecting the control office and the field station having a code transmitter relay at the control ofice, a code determining relay at the control office effective when energized in combination with the condition of said manually operable means to determine the respective code characters forming respective selected control codes for said device, circuit means for energizing said code determining relay in response to the actuation of said manually operable means, circuit means for energizing said code transmitter relay for each character of a particular type selected for transmission by said code determining relay and for deenergizing said code transmitter relay for each other type of character to be transmitted, a check relay at the control office, pick up circuit means for said check relay momentarily energized in response to actuation of said manually operable means, stick; circuit means effective to maintain said check relay energized during the transmission of code characters only so long as said. transmitter relay is actuated in correspondence with the respective types of code characters determined by said code determining relay and said manually operable means, means including said code communication apparatus and said check relay for applying distinctive characterization for transmission to the field station upon completion of the stepping at the end of a control cycle in case said check relay becomes deenergized during code transmission, and decoding means at said field station for causing the operation or" said device to its respective controllable conditions in accordance with the respective control codes received, said decoding means being rendered inefiective to govern said device in response to said distinctive characterization of the code communi-- cation apparatus.

'7. A centralized traffic control system for the communication of controls for a device having a plurality of distinctive controllable conditions from a control olfice to a field station comprising in combination, a manually operable multiple position selector at the control oflice for designation of respective controls to be communicated to the field station for said device, a line circuit connecting the control office and the field station, code communication apparatus including a code transmitter relay eilective by selective energization to when energized in combination with said manually operable selector to determine the respective code characters forming a control code for said device, circuit means for energizing said code determining relay in response to the actuation of said manually operable means, circuit means for energizing said code transmitter relay for each of a particular type or" character selected for transmission by said code determining relay and deenergizing said code transmitter relay for each other character, and check circuit means at the control office operable step by step to check continuity through said circuit means for the energization of said code transmitter relay, said check circuit means being effective to distinctively characterize the condition of said line circuit upon completion of the stepping at the end of each control cycle as compared to a normal control cycle whenever said code transmitting relay has failed to transmit a code character corresponding to the code selected by said code determining relay, decoding means at said field station for causing power operation of said device to its respective control conditions in accordance with respective control codes received, said decoding means being rendered ineffective for any control cycle in response to said distinctive characterization of the line circuit at the end of a control cycle, and indicating means at the control ofiice responsive to the actuation of said check circuit means.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,409,696 Lewis Oct. 22, 1946 2,452,589 McWhirter et al Nov. 2, 1948 

